Obesity epidemic increases global cancer burden

The review reported that excess body weight accounted for 3.9% of cancers worldwide in 2012 and for up to 30% of certain cancers, such as endometrial cancer. While the proportion dropped to under 1% in some low-income countries, it grew to 7–8% in high-income Western countries and MENA countries, which are home to a large fraction of the world’s obese population.

Population growth coupled with a greater frequency of obesity has led to a sixfold rise in the numbers of obese adults over the past four decades, from 100 million in 1975 to 671 million in 2016. Obesity is often associated with national wealth, but social norms, policy decisions, and environmental factors are also major drivers. “If the default option is adhering to an unhealthy lifestyle, such as eating junk food and not moving, that’s what people will do,” says author Kerem Shuval of the American Cancer Society; adding that, in the United States, “unhealthy foods are all around us, they are readily available and cheap, and we use cars to move around. This default option leads to the inevitable outcome of obesity.” By contrast, in countries such as the Netherlands, where policies and infrastructure encourage an active lifestyle, the default course of action leads to low obesity rates.

Sedentary lifestyles are becoming more common across MENA countries regardless of income, says Ali Shamseddine, a cancer researcher at the American University of Beirut Medical Center who was not involved in the review. “In low income countries, people are ditching their farming activities to work in cities where kids have less access to outdoor activities. In high income countries, the sedentary lifestyle results from access to entertainment and food choices as part of the more affluent lifestyle,” he says. This may explain the prevalence of obesity in lower income countries like Egypt, where 43% of women and 24% of men are obese.

Egypt also ranked highest in the proportion of cancers attributable to excess weight, with 8.2% of cancers in the country linked with obesity. Saudi Arabia, with 7.5%, was ranked third globally, and Jordan came in ninth place with 6.9%; six other MENA countries had rates above 6.5%, and the proportion was higher for certain cancer types. “In our study of cancer risk factors in Lebanon, we found that obesity was a main risk factor, with nearly a third of the cases of some cancers linked to obesity,” says Shamseddine. 

The authors call for policy interventions and environmental changes to reverse the obesity epidemic, highlighting strategies recommended by the World Health Organization in 2017. “Without high level policy/system changes, this problem will not go away,” says Shuval.

Shamseddine believes the recommendations could lead to promising results, but notes that “in this part of the world, political issues make the implementation of laws highly dependent on political leaders, regional conflicts, and economic crises.” Nevertheless, even small changes such as making sports mandatory in schools — they aren't at the moment, according to Shamseddine — could encourage better habits. Shuval says a more active lifestyle coupled with a return to traditional diets “would do wonders.”

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